Process for the production of rayon products



v value above 60 into United States Patent PROCESS FOR THE PRODUCTION OFPRODUCTS Nicolas Drisch and Paul Herrbach, Paris, France, as-

signors to Textile & Chemical Research Company, Ltd., St. Peter Port,Guernsey, Channel Islands, a corporation of Great Britain No Drawing.Application July 3,

Serial No. 297,180

Claims priority, application France January 15, 1952 8 Claims. (Cl.18-54) This invention relates to the production of viscose rayon,artificial horse-hair, ribbons and the like and particularly to theproduction of viscose staple fibre.

In co-pending application No. 193,746, now Patent No. 2,607,955, thereis described a process for spinning viscose having a viscosity of atleast 400 poises and a 'ycoagulating baths of low acid (e. g. sulphuricacid) concentration, the filamentary products being fixed by treatmentwith hot aqueous liquid.

The process described in the application has since been the subject oflong research, the remarkable results of which form the subject of thepresent invention, which relates to a modified process by means of whichit is possible to obtain fibres having a remarkably high resistance torepeated bending. The known processes 'for the production of rayon,including those described in the said co-pending application, do notenable fibres to be obtained which have as high a resistance to repeatedbending as is desired. Resistance to bending is of fundamentalimportance to the behaviour of artificial staple fibres during use andthe modified process of the present invention is therefore moreparticularly difected to the production of staple fibre. f;

It is an object of the present invention to provide artificialfilamentary materials of viscose which have a remarkably high resistanceto repeated bending. A further object of this invention is to provideartificial viscose staple fibre which has a high resistance to repeatedbending. A still further object is to provide processes whereby suchfilamentary materials and staple fibre? may be obtained. Another objectof the invention is'f-to provide a combination of a viscose spinningsolution and a coagulating bath of such compositions that the aforesaidproducts are obtained. Other objects of the invention will appearhereinafter.

It has been discovered that products of very high resistance to bendingcan be obtained, in processes using viscose of the aforesaid specialproperties and dilute acid coagulating baths by increasing the sodiumsulphate content of the coagulating bath. A content of sodium sulphateup to 25 g./litre in the coagulating bath is known, and results from thereaction between the caustic soda in the viscose and the weakly acidbath, taking into account the constant renewal of the bath.

It has now been discovered that the resistance to repeated bendingincreases substantially if the sodium sulphate content is increased toat least 50 grams per litre, and preferably to 80 to 150 grams perlitre, the upper limit being imposed by the solubility of the sodiumsul- YON As described in the co-pending application, it is essential touse cellulose pulp of very high degree of polymerisation, for example ofat least 700 to 800, and to conduct the preparation of the viscose underconditions such that the cellulosic material is depolymerised to aminimum extent. It should, for the purposes of the present inventionhave a viscosity of at least 300 poises and a 'y-value above 60 forsatisfactory spinning. Its cellulose content may be 4-8% or more. Thecaustic soda content may vary, but is preferably 35%, although it may behigher.

The following examples will serve to illustrate the invention but arenot to be regarded as limiting it in any way.

EXAMPLE I Linters of a degree of polymerisation of 700800 are mixed incaustic soda (concentration 225-240 g./litre) and pressed until theratio of the final weight of the alkali-cellulose to the weight of'y-cellulose contained in the pulp used is 2.8. The alkali-cellulose isnot ripened but is shredded and then xanthogenated with of carbondisulphide (calculated on the 'y-cellulose content of the pulp) atbetween 25 and 30. Degradation due to the action of atmospheric oxygenis limited to a minimum during the treatment, preferably by workingunder vacuum or in an inert atmosphere.

The cellulose xanthogenate is worked into a paste with concentratedcaustic soda at -5 to +S C. and the product is mixed with dilute causticsoda or water to produce a viscose containing 6% cellulose and 3% to 5%caustic soda. The viscose obtained is not aged. It has a -value above 70and ,a viscosity of about 400 poises.

It may be mentioned here that viscoses of high degree of polymerisationhaving viscosities substantially lower than 300 poises do not spinsatisfactorily.

The viscose is spun from a horizontal spinneret, the stream of fibresleaving the spinneret rising vertically in the spinning bath. A dilutesulphuric acid coagulating bath is employed which may contain up to 25grams per litre of sulphuric acid at room temperature. The sodiumsulphate content of the coagulating bath must be greater than 50 gramsper litre, and preferably greater than 80 grams per litre. The gelobtained following the coagulation is subject-ed to a stretch which mayvary between 30% and 150% according to the characteristics which it isdesired to impart to the thread. The gel is then treated with boilingwater to regenerate the cellulose.

Under these conditions, excellent spinning is achieved. The bundle offilaments is subjected to the usual finishing treatments and dried. Itmay be cut into lengths by means of a cutting machine before theregeneration treatment, or the finished bundle may be stretchedcontinuously until it breaks for the purpose of directly forming a phatein the slightly acid bath. baths contain 30 g./l1tre of sulphuric acid.

Table Fibre A Fibre B Fibre 0 Fibre D Fibre E Fibre F 30 g./l. 30 g./l.30 g./] 50 g./l. 115 g./l 115 g./] NBzSO4 NaaSOl N 1280 NazSOi NBzSOiNflzSOl Meancount 1 49 1 30 1 49 1 38 2 37 1 35 Percent; irregularity 4.7 7 6. 6 Rkm, dry 36. 2 23.1 28 32.1 31.3 33. 7 Rkm, wet 27 19 21. 3 25.6 24.1 27. 3 Dry elongation, percent 9. 2 7. 8 1i. 1 10. 5 13. 3 11. 7Wet elongation, percent 8.8 7. 3 14. 8 11 15.3 13 Quality factor 51 8285 93. 5 98. 1 D. P 583 488 406 517 610 Dye aifinlty 10 3 25 18Resistance to bending..... 270 566 700 870 2, 400 6, 620

It is pointed out that Rkm" is the kilometric length, that is to say,the length of fibre of the same type which must be suspended from thefibre to be tested in order to break it, and represents nine times thetenacity.

The quality factor is the wet tenacity multiplied by the square root ofthe wet elongation. The D. P. is the. mean degree of polymerisation. Theresistance to bending is measured as the number of bends before breakwith a load of 0.33- g. per denier.

The remarkable increase in by means of baths containing sulphate will beseen.

EXAMPLE ll Viscose is prepared under approximately the same conditionsas in Example I, with a cellulose content of 7% and a caustic sodacontent of 4%. The viscosity is 400 poises, the 'y is 75 and the D. P.of the cellulose in the viscose is 410.

This viscose is spun at room temperature into a bath of sulphuric acidwhich may contain up to 30 grams of sulphuric acid per litre, and whichcontains. inaddition 30 grams of sodium sulphate per litre in one case,and 100 grams of sodium sulphate in another case, with the usualstretching of the gel, acid cutting and decomposition in boiling waterfollowed by washing and finishing treatments under the usual knownconditions.

The fibres of 1.5 d. obtained have similar serimetric characteristicsnamely:

repeated beriding obtained large quantities of sodium Dry tenacity g./d3.4 Wet tenacity g./d 2.8 Dry elongation "percent" 10.5 Wet elongationdo 10.9

but in the first case it withstands 600 bending cycles, and in thesecond case 2000 bending cycles, the load being 0.33 g./d. as before.

These tests also confirm the very substantial improvement of theresistance to repeated bending due to the increase in the sodiumsulphate content of the coagulating bath.

We claim:

1. Process for the production of viscose rayon suitable for theproduction of staple fibre which comprises spinning viscose preparedfrom cellulose pulp having a degree of polymerisation or 700 minimum,without ripening the alkali-cellulose and without ageing of the viscose,the viscose having a viscosity of at least 300 pols-es, and; a gammahigher than 70, the coagulating bath employed comprising up to 25 grams/litre of sulphuric acid, and at least 50 grams per litre of sodiumsulphate.

2. Process for the production of viscose rayon suitable for theproduction of staple fibre which comprises spinning viscose preparedfrom cellulose pulp having a degree of polymerisation of 700 to 800,without ripening the alkali-cellulose and without ageing of the viscose,the viscose having a cellulose content of 4% to 8% and a caustic sodacontent of between 3% and a viscosity ot at least 300 poises, and agamma higher than 70, the coagulating bath employed comprising up tograms/- litre of sulphuric acid, and at least 80 grams per litre ofsodium sulphate. 1

3. Process for the production of viscose rayon suitable for theproduction of staple fibre which comprises spinning viscose preparedfrom cellulose pulp having a degree of polymerisation of 700 to 800,without ripening the alkali-cellulose and without ageing of the viscose,the viscose having a cellulose content of 4% to 8% and a caustic sodacontent of between 3% to 5%, a viscosity of at least 300 poises, and agamma higher than 70, the coagulating bath employed comprising up tograms/- litre of sulphuric acid, and at least grams per litre of sodiumsulphate, the viscose being spun vertically upwards from a horizontalspinneret.

4. Process for the production of viscose rayon suitable for theproduction of staple fibre which comprises spinning viscose preparedfrom cellulose pulp having a degree of polymerisation of 700 to 800,without ripening the alkali-cellulose and, without ageing of theviscose, the viscose having a cellulose content of 4% to 8% and acaustic soda content of between 3% and 5%, a viscosity of atlea s t 300poises, and a gamma higher than 70, the coagulating bath employedcomprising up to 30 grams/- litre of sulphuric acid, and at least 50grams per litre of sodium .sulphate, and subjecting the spun filamentaryproducts to high stretch continuously with their productron.

5. Process for the production of viscose rayon suitable for theproduction of staple fibre which comprises spinning viscose preparedfrom cellulose pulp having a degree of polymerisation of 700 to 800,without ripening the alkali-cellulose and without ageing of the viscose,the viscose having a cellulose content of 4% to 8% and a caustic sodacontent of between 3% and 5%, a viscosity of at least 300 poises, and agamma higher than 70, the

coagulating bath employed comprising up to 30 grams/- litre of sulphuricacid, and at least 50 grams per litre of sodium sulphate, and convertingthe spun filamentary products to staple fibre.

6. Process for the production of viscose rayon suitable for theproduction of staple fibre which comprises spinning viscose preparedfrom cellulose pulp having a degree of polymerisation of 700 to 800,without ripening the alkali-cellulose and without ageing of the viscose,the viscose having a cellulose content of 4% to 8% and a caustic sodacontent of between 3% and 5%, a viscosity of at least 300 poises, and agamma higher than 70, the coagulating bath employed comprising up to 30grams/- litre of sulphuric acid, and at least grams per litre of sodiumsulphate, the viscose being spun vertically upwards from a horizontalspinneret.

7. Process for the production of viscose rayon suitable for theproduction of staple fibre which comprises spinning viscose preparedfrom cellulose pulp having a degree of polymerisation of 700 to 800,without ripening the alhall-cellulose and without ageing of the viscose,the vis- 'cose having a cellulose content of'4% to 8% and a caustic sodacontent of between 3% and 5%, a viscosity of at least 300 poises, and agamma higher than 70, the coagulating bath employed comprising up to 30grams/litre of sulphuric acid, and at least 50 grams per litre of sodiumsulphate, the viscose being spun vertically upwards from a horizontalspinneret, and subieeting the spun filamentary products to high stretchcontinuously with their production.

8. Process for the production of viscose rayon suitable for theproduction of staple fibre which comprises spinning viscose preparedfrom cellulose pulp having a degree of polymerisation of 700 to 800,without ripening the alkali-cellulose and without ageing of the viscose,the viscose having a cellulose content of 4% to 8% and n caustic sodacontent of between 3% and 5%. a viscosity of at least 300 poises, and agamma higher than 70, the coagulating bath employed comprising up to 30grams/- litre of sulphuric acid. and at least 50 grams per litre ofsodium sulphate, and subjecting the spun filamentary products to highstretch continuously with their production. and converting the spunfilamentary products to staple fibres.

References Cited in the file of this patent UNlTED STATES PATENTS Drischet al June 13, 1950 Drisch et al. Aug. 26, 1952 OTHER REFERENCES

1. PROCESS FOR THE PRODUCTION OF VISCOSE RAYON SUITABLE FOR THEPRODUCTION OF STAPLE FIBRE WHICH COMPRISES SPINNING VISCOSE PREPAREDFROM CELLULOSE PULP HAVING A DEGREE OF POLYMERISATION OF 700 MINIMUM,WITHOUT RIPENING THE ALKALI-CELLULOSE AND WITHOUT AGEING OF THE VISCOSE,THE VISCOSE HAVING A VISCOSITY OF AT LEAST 300 POISES, AND A GAMMAHIGHER THAN 70, THE COAGULATING BATH EMPLOYED COMPRISING UP TO 25GRAMS/LITRE OF SULPHURIC ACID, AND AT LEAST 50 GRAMS PER LITRE OF SODIUMSULPHATE.